Formation of Z-Phase Particles in a Martensitic 9% Cr Steel during Creep at 650°C and Their Influence on the Creep

Abstract

Abstract—The mechanism of the nucleation of Z-phase (CrVN) particles in a martensitic 10Kh9K3V2MFBR steel (9 wt % Cr) during creep at a temperature of 650°C is studied. The nucleation mechanism of Z-phase particles at a creep temperature of 650°C is found to be restructuring of the crystal lattice of V(C,N) carbonitrides due to the diffusion of chromium atoms. The transformation of nanosized V(C,N) carbonitrides into Z-phase particles is shown to weakly contribute to the structural degradation in the steel and not to cause its premature fracture during creep at 650°C if at least 50% V(C,N) carbonitrides of the initial volume fraction of these particles are retained (even at a large average size (≈200 nm) of Z-phase particles).